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Zeros Or Roots Modules

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CALCULATOR MODULE : Maths Polynomial   ±

Calculate polynomial coefficients, roots or zeros, maximum and minimum, points of inflection, and interpolate polynomial value, slope and curvature.

Polynomials can be calculated for linear (first order), quadratic (second order), cubic (third order), quartic (fourth order), quintic (fifth order), sextic (sixth order), septic (seventh order), octic (eighth order) or nth degree. For polynomials with all real roots, all roots can sometimes be solved simultaneously using the Durand Kerner method. In other cases solve for individual roots. The maximum or minimum points (slope equals zero) and the inflection points (curvature equals zero) can also be calculated. Use a plot page to plot the polynomial and identify the approximate root values if any.

Lagrange's method is used to interpolate between data points. This method is useful for interpolating between data points, but can give poor results when extrapolating outside the data range. Evenly spaced data points can result in cyclic behaviour.

Polynomial coefficients can be calculated from the real roots, and the nth coefficient. There are an infinite number of polynomials with the same roots. The nth coefficient is required in order to calculate unique coefficients. This method only applies if all of the roots are real. Polynomial coefficients can also be calculated from XZ data points.

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CALCULATOR MODULE : User Programmable   ±

Use the user programmable calculator to write your own programs, with inbuilt plots and tables etc. Select the number of X input variables and Z output variables on the setup page. For example if you have one equation with two input variables select two X input variables, and one Z output variable.

The calculators use Javascript so you can use the full range of programming constructs: if, else, for, while. You can also define functions and objects to use in your code. Enter Javascript statements to define all of the output variables z1, z2, z3... in terms of the input variables x1, x2, x3.... and any previously defined variables. Each Javascript statement should be on a new line and must end with a semi colon ';' eg : z1 = x1 + 2 * x2;. You can also reference the variables by index eg: for(i=0: i<3; i++){x[i] = sin(z[i]);}. Refer to the help page in Resources for more details.

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    CALCULATOR MODULE : JONSWAP Wave Velocity And Period   ±

    Calculate JONSWAP wave seabed velocity and zero upcrossing period from spectral moments.

    The seabed velocity and upcrossing period is calculated using a first order Airy wave transformation. The Airy wave transformation may not be valid in shallow water. The calculation has been optimised for elevations on or near the seabed, and is not recommended for elevations greater than half the water depth. Return period data can be analysed using either the Weibull, Gumbel or Frechet distribution.

    Reference : Hasselmann K et al : Measurements of Wind-Wave Growth And Swell Decay During The Joint North Sea Wave Project (JONSWAP)

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